1. Field of the Invention
The present invention relates to a linear compressor, and more particularly, to a linear compressor including a suction valve stopper, which limits the degree of opening of a suction valve when the suction valve performs an opening operation.
2. Description of the Related Art
Generally, a linear compressor is an apparatus configured in such a fashion that a piston reciprocates in a cylinder upon receiving a reciprocating drive force of a linear motor to compress working-fluid, for example, refrigerant, received in the cylinder. The linear compressor is mainly used in refrigerators, etc.
FIG. 1 is a sectional view illustrating a conventional linear compressor. FIG. 2 is a view of important parts of the conventional linear compressor, illustrating the advance movement of a piston. FIG. 3 is a view of important parts of the conventional linear compressor, illustrating the retraction movement of the piston.
As shown in FIGS. 1 to 3, the conventional linear compressor comprises a shell 2 forming the outer appearance of the compressor, a cylinder block 4 and a back cover 6 which are arranged in the shell 2, and a compression unit provided between the cylinder block 4 and the back cover 6. The compression unit serves to compress working-fluid by a desired compression ratio.
The shell 2 is provided with a fluid suction pipe 8 and a fluid discharge pipe 9, such that the working-fluid to be compressed is sucked into the compression unit from the outside of the shell 2, and then, is again discharged out of the shell 2 after being compressed in the compression unit.
The compression unit includes a cylinder 10 into which the working-fluid, having passed through the fluid suction pipe 8, is sucked, a piston 20 to compress the working-fluid sucked into the cylinder 10 while performing reciprocating movements in the cylinder 10, and a linear motor 30 to reciprocally move the piston 20.
The cylinder 10 is provided with a discharge valve assembly 12, such that the working-fluid, compressed in the cylinder 10, is discharged into the fluid discharge pipe 9 in accordance with the operation of the discharge valve assembly 12.
The piston 20 is internally formed with a suction path 21 for allowing the working-fluid, having passed through the fluid suction pipe 8, to be sucked into the cylinder 10. Also, the piston 20 has a suction valve 22 to open or close the suction path 21.
The suction valve 22 is an elastic member fastened to the piston 20 by means of a bolt B. The suction valve 22 is designed to be opened or closed as it is elastically deformed in accordance with a pressure difference between the suction path 21 of the piston 20 and the interior of the cylinder 10.
The linear motor 30 basically includes a stator 32, and a mover 34. The mover 34 is adapted to reciprocally move while electromagnetically interacting with the stator 32. The mover 34 is connected to the piston 20.
The compression unit further includes a main spring assembly 40 for providing the piston 20 with an elastic force in a reciprocating movement direction of the piston 20. Thus, the main spring assembly 40 allows vibrations of the piston 20 to some extent when the piston 20 reciprocally moves.
The main spring assembly 40 consists of a first main spring 42 located between the back cover 6 and the piston 20, and a second main spring 44 located between the cylinder 10 and the linear motor 30 to be supported by the cylinder block 4 and the piston 20.
The operation of the conventional linear compressor having the above-described configuration will now be explained.
If the linear motor 30 is driven, the piston 20 reciprocally moves in the cylinder 10 upon receiving the drive force of the linear motor 30. Then, the first and second main springs 42 and 44 are repeatedly compressed and tensioned in accordance with the reciprocating movements of the piston 20, thereby serving to allow vibrations of the piston 20 to some extent while causing the discharge valve assembly 12 and the suction valve 22 to be repeatedly opened or closed.
Thereby, the working-fluid is sucked into the cylinder 10 through the fluid suction pipe 8, such that it is compressed to a high-pressure state by the piston 20 in the cylinder 10. Subsequently, the compressed working-fluid is discharged from the cylinder 10 through the discharge valve assembly 12, to be discharged out of the shell 2 through the fluid discharge pipe 9.
The suction, compression, and discharge operations of the working fluid as stated above are continuously repeated in this sequence so long as the linear motor 30 is driven.
A problem of the above-described conventional linear compressor is that the suction valve 22 may be excessively opened due to a large pressure difference between the suction path 21 of the piston 20 and the interior of the cylinder 10, as shown in FIG. 3. This causes an increased stress to be applied to the suction valve 22, and therefore, there is a risk of plastic deformation or damage to the suction valve 22.
When the suction valve 22 exhibits such an excessively large degree of opening, an increased shock must be applied to the piston 20 when the suction valve 22 is closed, resulting in an increase in vibration and noise.
The degree of opening of the suction valve 22 may be changed in accordance with a pressure difference between the suction path 21 of the piston 20 and the interior of the cylinder 10. Therefore, an uneven amount of the working-fluid is sucked into the cylinder, making it impossible to achieve improved constant compression efficiency.
In particular, recently, environment-friendly nitrogen dioxide refrigerant has been widely used as the working fluid. However, when working-fluid is nitrogen dioxide refrigerant, the working-fluid exhibits a relatively high working pressure, causing more severe stress to be applied to the suction valve 22.